The invention relates to a dwell relay which provides a first output which increases, in response to an increasing input, from a first reference level to a second reference level whereat the first output will increase no further and a second output which decreases, in response to further increases in the input, from a third reference level to a fourth reference level wherein the increasing and the decreasing outputs are separated by a dwell period.
A dwell relay which has both an increasing output and a decreasing output separated by a dwell period can have many useful applications. For example, in the control of a heating and air conditioning system the increasing output can be used to control the heating coil and the decreasing output can be used to control a cooling coil such that if the output of the dwell relay is in the dwell period neither heating nor cooling is provided. The dwell period in which neither heating nor cooling is provided can be made as long as comfort requirements permit to save energy during this time in which neither heating nor cooling is provided.